1. Field of the Invention
The present invention relates to a double-acting or lift and force pump for ejecting a product from a container, with a housing in which a piston with an axial bore is axially slidable and sealed by a first housing portion, with a hollow piston rod which extends the axial bore of the piston and is slidable in an opening of a closing cap of the housing and container, wherein the hollow piston rod has at its free end a tightly fastened actuating head, wherein, when the actuating head is actuated, the piston builds up a pressure against the force of a restoring spring in a pressure chamber of the housing, wherein an outlet duct connected to the bore extends through the actuating head and through a check valve up to an ejection opening for the product, and with at least one opening in a second housing portion between the first housing portion and the closing cap.
2. Description of the Related Art
A double-acting pump of this type disclosed in DE 27 09 796 B2 is suitable for ejecting or spraying a product out of a container, but is not suitable for ejecting or dispensing individual drops of a liquid, particularly not in an upside down position, as it is frequently required for dispensing liquid medicaments which are to be introduced drop by drop, for example, into the eyes, ears or nose.